Generator overload stop



April 5, 1932. A. F. BROTZ GENERATOR OVERLOAD STOP 1925 2 SheetsSheetFiled March 28 Etc; .1

M l o m w m 5 R 1 0 am V 50 55/ ATTRNEY A. F. BROTZ 1,852,835

GENERATOR OVERLOAD STOP April 5, 1932.

Filed March 28, 1925 2 Sheets-Sheet 2 2 FIG.

and power plants Patented Apr. 5, 1932 UNITED STATES PATENT OFFICE ANTONFRANK BROTZ, OF KOHLER, WISCONSIN, ASSIGNOR TO KOHLER COMPANY, OFKOHLER, WISCONSIN, A CORPORATION OF WISCONSIN GENERATOR OVERLOAD STOPApplication filed March 28, 1925. Serial No. 19,117.

This invention relates to generator overload stops for gas engineoperated generators and has for its object to provide means forautomatically stopping the operation of the 5 generator when the loadbecomes excessive.

Although not confined thereto, the invention is particularly designedfor use with automatic self-starting and stopping internal combustionengine driven farm lighting and consists in providing a generator havinga voltage control characteristic under which the speed of the generatorincreases with the load and a cut-out sensitive to the speed, the objectof the 1nvention being to stop the engine upon the occurrence of anoverload.

An object of the invention is to stop the operation of the generatingunit when overloaded and compel attention and removal 0 the overloadcondition by requiring the cutout to be reset before operation isresumed.

Another object of the invention is to provide an ignition controllingswitch actuated by a centrifugally operated means whereby the switchwill render the ignition circult inoperative to stop the engine when theload becomes excessive.

Another obiect of the invention is to perfect details of construction ofsuch an ignltion cut-out switch and the centrifugal operating meanstherefor.

.With the above and other objects in v1ew the invention consists in thegenerator overload stop as herein claimed and all equivalents.

Referring to the accompanying drawlngs in which like characters ofreference indicate the same parts in different views,

Fig. l-is a diagram of the circuits of a gas-engine-operated generatingsystem with which the generator overload stop of this invention issuitable for use and showing the ignition circuit controlled by thecut-out;

Fig. 2 is a sectional elevation of the gas engine through the fiy-wheelof the gas engine, showing the cut-out switch and the centrifugaloperating means therefor in their assembled relation; 7 ,Fig. 3 is asectional view on the plane of line 33 of Fig. 2 and showing by the line22 the sectional plane-of Fig. 2;

Fig. 4 is an enlarged sectional view on the line 44.- of Fig. 2 showingthe relation of tliie cut-out switch and its centrifugal opera or;

Fig. 5 is a detailed sectional View of the cut-out switch in its closedposition for stopping vthe engine, its other position being shown indotted lines, and

Fig. 6 is a perspective view of the springpressed operating means forthe cut-out switch.

In these drawings, 10 indicates a generator driven by an internalcombustion engine 9, the throttle valve 11 of which is controlled by asolenoid having windings connected with the generator windings, as willbe described.

f The generator, as shown, is of the shunt type and supplies the mains12 containing lamps 13 or other translating devices. The shunt fieldwinding 14: of the generator is opposed by a bucking series fieldwinding 15, which becomes stronger as the load on the mains increasesand thereby opposes a greater influence to the shunt field to weaken thefield strength. At the same time a series coil 16, also in the loadcircuit and strengthened by the increasing load, opposes to a greaterextent the influence of a shunt or voltage coil 17 to effect a furtheropening movement of the throttle valve of the engine to increase thespeed of the engine.

The solenoid is so constructed that the voltage coil .17 of many turnsof fine wire connected in parallel with the shunt field 14 and thecurrent or series coil 16 of few turns of large wire in the loadcircuittogether act upon the core 21 but in opposition s' to each other.The solenoid core is pivotally connected to the shorter arm ofabell-crank lever 23, the other arm of which is connettedby a link 27with the throttle 11 so that in the extreme upper position of the core,as when the generator is not operating and the coils are therefore notenergized, the throttle is held in an open position. The core is held inthis position by a compression coil spring 25 which afi'ords a yieldingresistance to the operation of the solenoid core.

When the generator is started with a minimum load or no load on theservice mains, the series coil 16 opposes the voltage coil 17 onlyslightly or not at all, and the core will be drawn to a lower positionagainst the action of spring and will move the throttle to a positionpartially closing the mtake manifold of the engine, so that the engineoperates at a minimum speed under which the generator develops the linevoltage. As the load increases the generator field is weakened by thebucking series field 15, as above mentioned, and the influence of thebucking current coil or series coil 16 becomes greater, tending toneutralize the influence of the voltage coil 17 and permit the spring 25to hit the core and move the throttle toward its open position, thusincreasing the supply of fuel to the engine to increase its speedcorresponding with the increase in the load.

The proportioning of the field wlndin of the generator and of the coilsof the solenoid and of the throttle and its operating means,

is made to compensate for a change in load by causing a change in speedwithout a material change in voltage developed by the enerator. Theweakening of the generator eld by the bucking coil 15 serves tofacilitate the increasing of the speed of the engine caused at the'sametime by the bucking influence of the series coil 16 of the solenoidopening the throttle, and this bucking field winding exaggerates thespeed variation characteristic of the generator for constant voltageconditions so that the desired object is accomplished of materiallyreducing fuel consumption to correspond with a reduction of load.

For increased independent regulation a resistance is connected in serieswith the shunt field winding 14 of the generator and wires 31 and 32connect the ends of this resistance with switch contacts 33 and 34,respectively, of a resistance short-circuiting switch operated by asolenoid which is connected across the terminals of the generatorpreferably with a resistance 51 in series therewith. Thus the fieldregulating resistance short circuit is controlled by a switchindependent of the throttle-controlling solenoid but sensitive to thevariation in voltage developed by the generator. Being independent it isnot affected by the spring adjustment of the solenoid core.

By this arrangement the momentary rise in voltage when the load issuddenly reduced from full load to minimum load is prevented, the suddenweakening of the bucking current coil 16 accompanied by a slightstrengthening of the voltage coil 17 being sufficient to cause the core21 to move to the position for closing the throttle. At the same timethe voltage coil 50, because of its momentary rise in voltage, opens thecontacts 33 and 34, thus break ing the short circuit around theregulating resistance 30 including this resistance in the shunt fieldwinding to weaken the fields and check the rise in voltage. Suchtendency to abnormal voltage is only momentary and as soon as the speedof the generator has reduced to correspond with the new throttleposition, the normal conditions are restored the throttle position beingdetermined by the differential solenoid 16-17 and the field resistanceshort-circuiting switch being permitted to close by the voltage coil 50.

As so far described the system is like that covered by my applicationfor voltage regulators, Serial No. 656,334, and is only given in detailherein in order to exemplify the class of generating units chosen foruse with a speed-sensitive ignition cut-out to constitute the generatoroverload cut-out because the characteristic is present of an increasingspeed with an increasing load.

It has been found in practice that with all farm lighting plantgenerating systems in the hands of unskilled operators there is atendency to increase the load beyond the rated capacity attended by thedanger of possible damage and to prevent this practice the presentinvention provides for automatically stopping the engine when the loadbecomes excessive.

The gas engine 9 may be of the air cooled type having a blower fanincorporated with its fly wheel 61 to draw air through passagewaysaround the cylinders and the ignition may depend upon a magneto alsoincorporated in the fly wheel as shown, though these features are notessential to the invention.

As shown, the magneto comprises a stationary coil 62 having arc-shapedpole pieces 63 fixed on studs 64 projecting from a removable cover plate65 for the crank-case of the engine, which cover plate also carries thebearing 66 for the crank shaft 67. The arcshaped permanent magnets 68are carried by a ring 69 of non-magnetic material, which is clamped onthe fly wheel by screws 70, and pole pieces 71, also clamped on the ring69 by screws 72, travel around and close to the pole-pieces 63 of thestationary magnet 62, there being primary and secondary lead wires 7 3and 7 4 respectively, extending from the coil 62 to the usual breakerand distrib uter shown in diagram Fig. 1.

The ignition cut-out of this invention which is to render the ignitionineffective when the generator is subjected to an excesssive loadcomprises a cut-out switch member for grounding the primary of themagneto. This member, as best seen in Fig. 5, constitutes a leverfulcrumed at 7 6 between ears of a metal block 77, which is secured tothe inner side of the casing 78 of the engine by screws 79, said leverbeing of angular shape with its end extending through an opening in thecasing with a knob 80 outside the cas ing, which, indicates; theposition bf the switch and'serves as the means for resetting the switchafter .it has been, automatically operated, as will be explained. d i

The switch lever 75 is held by spring pressure in. either its innerposition or its outer position by a bow sprin 81 fitting at one end in anotch in the end block 77 and at the insulated from the bloc'k7 7. Inthe form shown the contact consists of a rivet passing through areducedportion of the block 7 7 primary lead 7 3 of the magneto leading to thewith insulating washers to protect .it from electrical connection withsaid block and with a connecting plate 84 connected bya wire 85-with'the-circuit breaker, said wire 85 and the same-binding post of thecircuit breaker for convenience. It will be seen that, inasmuch. as thelever is grounded on the casing through the block 77, its contact withthe contact 83 serves to ground the ignition lead and thereby render themagneto inefiective .for producing ignition in the well known manner.

The normalposition for the cut-out switch lever 75 isits inner position,shown by dotted lines in Fig. '5, but a centrifugally operated means isprovided for engaging it and throwing it to-its outer position to'groundthe magneto automatically when a predetermined speed is attained, thatis when the generator is overloaded. 5 Such operating means may consistof an arm 86 pivotally mounted on the side ring of the blower fan 60 andheld with spring pressure in a normalinner position where its laterallyextending rounded proj ection 87 clears the angular bend or elbow of thecut-out lever 75,'the weight of said. arm, however. being suflicient tocause it to swing outwardly against the. pressure of its springto'engage the lever 75 and move it to its outer position to ground themagneto when an ex cessive speedis reached. Q

In detail the arm 86 has a side lug 88 bent up at right angles to it inavertical'plane and in an opening of said lug is-a loose bushing 89.slightly thicker than the lug, as seen in Fig. 4, to afl'ord a freebearing for the arm when said bushing is clamped to the side ring of theblower 60 by means -of a bolt'90 with washer 9 1. A leaf spring-92' isriveted to the arm near its lug and bears against one of the blades ofthe blower fan, asseen' in Fig. 2, the inward movement of the arm beinglimited by its engagement with another blade of the blower fan and theouter movement by a stop lug 93 bn its end engaging the spring.

' In operation the cut-out lever 75 being in its inner position, theignition system is effective for operating the engine, but upon afailure of the voltage regulator to properly control the speed of theengine so that the engine races or exceeds its predetermined speed, thecentrifugal force acting upon the arm moves it outwardly until itslateral rounded projection 87 strikesthe lever 75 and throws lit to itsouter position, where it is held by the -spring 81 in engagement withthe contact 83 toground the magneto and thereby render the ignitionineffective so that the engine stops. Although the system with which theignition cut-out of this invention is used is ofothe demand "startertype, the continuance of the load on the mainsis incapable of againstarting the unit in operation until the at-- tendant resetstlie cut-outswitch lever 75 to remove the ground connection from the magneto, thusinsuring that proper'inspection will be made and the overload removed ordefect remedied to prevent a recurrence of the "excessive speedbeforethe system is again started.- While the invention has beendescribed i connection with a particular gas-engine-operated lightingand power unit wherein magneto ignition is relied on, it is not limitedto such use but may be used in any system wherej in it is desired tostop the operation of a gas engine or the like whether dependin onmagneto ignition or battery ignition, it eing understood that the usualmodification is implied for battery ignition control whereby the batterycircuit s opened to be rendered inoperative instead of being-grounded bythe operation ofthe cut-out switch lever.

What I claim as new and desire to secure by Letters Patentis:

1. A generator overload cut-out comprising a ga's-engine-drivengenerator and its ignition circuit a voltage regulator increasing thespeed of the generator with an increase of the load, a centrifugallyoperated arm driven by the engine, an ignition cut-out switch in thepath of the arm to be engaged thereby in the position of the arm asopenand a closed position and being moved 'from one position to the other bythe engagement of the arm therewith, and a spring u'rg ing the cut-outswitch to either of its positions, saidcut-out switch serving to controlthe ignition circuit.

2. A generator overload cut-out comprising a gas-engine-driven generatorhaving its speed v'arymg with the load, an arm pivotally mounted on thefly wheel of the engine,

and-an ignition cut-out'switch mounted on the casing of the gas engine,said switch comthe occurrence of an overload on the mains or prising apivotally mounted switch lever within the engine casing and projectingthrough an opening thereof and adapted to be engaged by the arm andhaving an inner and an outer position, a spring for holding the lever ineither of its positions, and -a contact engaged by the lever when it ismoved to its outer position for rendering the ignition circuit of theengine ineffective.

3. A generator overload cut-out comprising a gas-engine-driven generatorhaving its speed varying with the load, an arm pivotally mounted on thefly wheel of the engine, a spring for holding the arm in an innerposition but yielding to permit the arm to swing outwardly under theaction of centrifugal force, a block mounted within the engine casing, alever pivotally mounted thereon with its end passing through an openingin the casing and having an inner and an outer position, the innerposition being in the path of the arm when it is moved outwardly bycentrifugal force, a bow spring connecting the lever and the block,acontact on the block engaged by the lever, and an ignition magneto forthe engine having its primary winding connected with the contact wherebysaid magneto is grounded by the lever in its outer position.

4. Means for preventing subnormal voltage operation of gas-engine-drivengenerator units of the demand-responsive type by stop ping the unit uponthe occurrence of an overload, comprising, in combination with suchunit, engine throttle controlling means sensitive to the load increasingthe speed as the load increases, and a centrifugal ignition cutoutresponsive to such increase of speed.

5. Means for stopping a generator upon the occurrence of an overload onthe mains, comprising a gas-engine-driven generator, engine controllingmeans for increasing the speed thereof when the load increases, anddisabling means for the gas engine dependent on the speed.

6. Is a gas-engine-operated generator, automatic means for opening thethrottle of the engine to increase the speed as the load increases, andan ignition cut-out responsive to such increase of speed.

7. The method of protecting a gas-engineoperated generator fromoverloading, consisting of increasing the speed when the load increasesand discontinuing ignition upon attaining a predetermined speed.

In testimony whereof I afiix my signature.

ANTON FRANK BROTZ.

